Measuring device for the optical analysis of a test strip

ABSTRACT

The invention concerns a measuring device for the optical analysis of a diagnostic test element ( 10 ) comprising a light source ( 16 ), a photodetector ( 24 ) and a device ( 12 ) for positioning the test element ( 10 ) between the light source ( 16 ) and photodetector ( 24 ) where the light source ( 16 ) has one or several organic light-emitting diodes (OLEDs) and the OLEDs ( 14 ) for a composite structure with an imaging optics ( 20 ) and/or a photodetector ( 24 ) by means of a support substrate.

The invention concerns a measuring device for the optical analysis ofespecially a test element diagnostic test element comprising a lightsource, a photodetector and a device for positioning the test element inan optical path between the light source and photodetector.

Analytical systems of this type are used in medical diagnostics in orderto optically examine a disposable test strip that can be loaded with ananalyte for example for colour changes. The photometric arrangement thatis required for this in a measurement module that may be used by thetest subject himself requires an exact orientation of the individualcomponents in order to achieve the desired performance. In themanufacturing process the light source, optical system and detector areusually assembled in large numbers by so-called pick and placeprocesses. This can only be carried out with a limited degree ofaccuracy and reproducibility and becomes the more time-consuming thesmaller the components are and the smaller the optical manufactured sizeand focal length that is available.

In the case of display elements in electronic devices it is known thatdisplay pixels can be formed on the basis of organic light-emittingdiodes (OLED) which in contrast to conventional inorganic LEDs that arebased on crystalline semi-conductor structures, can be manufactured overa large area as very thin flexible flat emitters.

On this basis the object of the invention is to improve a measuringdevice of the type described above and in particular to achieve a simplecompact design with a high manufacturing and measuring precision.

The combination of features stated in claim 1 are proposed to achievethis object. Advantageous embodiments and further developments of theinvention are derived from the dependent claims.

The basis of the invention is the idea of creating a solid composite oflight source, optical system and/or detector. Accordingly the inventionproposes that the light source has one or more organic light-emittingdiodes (OLEDs) and the OLEDs form a composite structure over a supportsubstrate with an imaging optical system and/or the photodetector.

This allows a simplified batchwise manufacture with a high, uniformpositioning precision of the components and a low manufacturingvariation. The manufactured size can be considerably reduced due to theplanar construction of at least the light source. The use of OLEDs givesrise to a wide variety of advantages such as high luminosity with arelatively low energy consumption, wide viewing angle, potentially lowmanufacturing costs and reduction of material costs and a productionprocess that can be automated on a large scale to manufacturephotometric modules for analyzers.

The use of OLEDs gives rise to further unexpected advantages compared toconventional LED light sources in photometric measuring units: It ispossible to vary the design of the light source which can be optimizedfor the photometric arrangement. As a result of the homogeneous lightdistribution over the OLED surface, the imaging optics can be improvedwithout requiring an adaptation with regard to shadowing electrodes aswould be the case for conventional LEDs. The substantial lowertolerances in the distance between the optical system and light sourceand in the lateral positioning accuracy makes it more possible tocollimate the measuring light in order to illuminate the test field in amanner which is substantially independent of distance. Even if it is notpossible to achieve a perfect collimation, there is at least a lowersensitivity towards distance tolerances.

Moreover, the low positioning tolerance in the composite structureallows a small focal length which enables a more efficient operation. Inparticular this allows measurement on the emitter side with a low powerrequirement or an improved signal-to-noise-ratio on the receiver side.

Advantageously a plurality of OLEDs are arranged on the supportsubstrate as a one-dimensional or two-dimensional light-emitting pixelarray. In this connection the OLEDs can have different emissionwavelength ranges and/or preferably be aligned in a grid-like manner ondifferent lighting target areas. This enables a spatially resolvedlighting in order to localize the target area for example in the case ofmicroscopic quantities of sample or to carry out additional analyses.

The OLEDs can be constructed in one-dimensional compactness from twoelectrode layers and a sandwich-like intermediate electroluminescentlight-emitting layer that is preferably formed from a polymer material.This enables a pixel size of less than 500 μm, preferably less than 200μm to be achieved.

An advantageous embodiment envisages that the OLEDs have a transparentfront electrode layer adjoining the substrate for radiating lightthrough the substrate and a rear electrode layer that faces away fromthe substrate. In this connection the front or the rear electrode layercan be formed or contacted jointly for all OLEDs while individual pixelscan be separately controlled by a single electrode opposing each pixel.

The imaging optics preferably has at least one optical lens to form animage of the light source on a target area of the test element and/or animage of a target area of the test element on the photodetector.

For a further integration it is advantageous when the imaging optics hasa plurality of microstructured, preferably aspherical lens units in atwo-dimensional arrangement. This imaging optics is preferably formed bya lens structure moulded on the support substrate especially byembossing. Alternatively it is also possible that the imaging optics isformed by a foil material, preferably a polymer-based foil materialhaving a lens structure that is preformed especially by embossing (hotstamping or injection stamping), injection moulding or reaction mouldingthat is joined to the support substrate in a planar fashion.

A compact structure with a favourable optical path is achieved byarranging the OLEDs on one side of the support substrate and the imagingoptics on the opposite side of the support substrate. The supportsubstrate should consist of a transparent flat material especially of athin glass or a polymer film.

Another preferred embodiment of the invention envisages that thephotodetector is formed by at least one layer-shaped organic photodiode.This further improves the positioning of the optical components wherethe layered deposition of light emitter and receiver is alsoadvantageous with regard to an integrated manufacture.

A plurality of organic photodiodes are advantageously arrayed on thesupport substrate as a linear or planar sensor pixel array to enable aspatially resolved scanning. In another advantageous embodiment aplurality of OLEDs and photodiodes that are locally combined as anelementary photometer and are arranged as a matrix on a surface of thesupport substrate, form a multiple photometer.

Another improvement provides that the device for positioning comprises aholder, a guide or a stop for the test element. The device forpositioning can also comprise a test element holder that can be movedbetween a loading position and a measuring position.

In order to increase the durability it is advantageous when the surfaceof the OLEDs is screened from the environment in a material-tight mannerby a coating or housing.

Another advantageous embodiment provides that the test element is formedby a test strip provided with optically scannable indicator fields forbiological substances to be detected and especially a test stripdesigned as a disposable article for example a glucose test strip.

The invention is further elucidated in the following on the basis of anembodiment shown in a schematically simplified manner in the drawing.

FIG. 1 shows a photometric measuring device as a composite structure oforganic light-emitting diodes and photodiodes as well as imaging opticsfor analysing diagnostic test strips in a sectional drawing;

FIGS. 2 and 3 show further embodiments of organic light-emitting diodesand their associated imaging optics in cross-section;

FIG. 4 shows a hermetically screened organic light-emitting diodearrangement in a housing in cross-section and

FIG. 5 shows a matrix arrangement of single photometers based oncombined organic light-emitting diodes and photodiodes in a top-view.

The optical measuring device shown in the diagram serves tophotometrically analyse or evaluate diagnostic test strips 10, forexample for glucose tests in blood samples. It comprises a positioningunit 12 for the test strips 10 and a composite structure consisting of alight source 16 formed by at least one organic light-emitting diode(OLED 14), a support substrate 18, an imaging optics 20 and aphotodetector 24 having at least one polymer photodiode 22.

In the embodiment shown in FIG. 1 several OLEDs 14 arranged in amatrix-like manner are provided which have different emissionwavelengths. The film-like OLEDs 14 are based on at least one thinorganic light-emitting layer 26 which is arranged in a sandwichformation between two electrode layers 28, 30. When a voltage isapplied, positive charges are displaced from the anode layer 28 into thelight-emitting layer 26, while electrons are injected onto the cathodelayer 30. As a result of the electrical field, the injected chargecarriers each move to the opposite electrode layer. If electrons andholes meet, electron-hole pairs are formed which can recombine whileemitting radiation. The emission spectrum is determined by the organicsemiconductor material that is used. Highly efficient OLEDs containfurther injection and transport layers to optimize this injectionelectroluminescent effect and auxiliary layers as diffusion barriers andfor homogenization.

In the embodiment of FIG. 1 a common anode 28 adjoining the supportsubstrate 18 is provided which is composed of ITO (indium-tin-oxide) orrelated oxidic compounds as well as conducting polymers and is permeableto the emitted light. In contrast the cathodes 30 consisting of a metallayer can be individually controlled by separate pick-ups 32.

The different wavelengths of the controlled OLEDs enable differentoptically detectable reactions or properties of the analytical testareas 34 to be evaluated on the test strip 10. In addition the matrixarrangement of the OLEDs enables different illumination target areas orillumination spots to be irradiated in order to for example examine verysmall sample volumes on a given test area 34 in a spatially resolvedmanner.

The support substrate 18 is composed of a thin flat material that ispermeable to the generated light and in particular a thin glass orflexible polymer film or a suitable multilayer. The OLEDs 14 that aremounted thereon can be manufactured as layer emitters in extremely smalldimensions. For example the pixel size can be between 50 and 200 μmwhereas the layer thickness of the light-emitting layer 26 can be in therange of 100 nm. Such structures can be produced with high precision bya variety of process techniques such as dipping methods, spin and dipcoating, sieve and inkjet printing, PVD and CVD methods.

The imaging optics 20 is mounted on the side of the support substrate 18that is opposite to the OLEDs 14. It has a plurality oftwo-dimensionally distributed lens units 36 to couple out the measuringlight on the emitter side and couple in the measuring light on thedetector side. They can be laminated onto the side of the substratefacing the test element 10 as a prefabricated microstructured lensstructure 38 for example in the form of a hot-stamped film material.Alternatively the lens structure can be directly moulded onto the freesubstrate side for example by embossing.

Like the OLEDs the polymer photodiode 22 is a sandwich structurecomposed of two electrode layers 40, 42 and a semiconducting polymerlayer 44. Such photo-sensitive layer cells are known and described forexample in the publication of Dey et al., A dye/polymer based solidstate thin film photoelectrochemical cell used for light detection,Synthetic Metals 118 (2001), p. 19-23 the contents of which are herebyincorporated.

Instead of a single photodiode 22, it is also possible for a pluralityof photodiodes to be arranged on the support substrate 18 as aone-dimensional or two-dimensional array or diode field. It is alsoconceivable that a conventional photometric receiver is combined with anOLED light source as described above.

The composite structure comprising OLED 14, imaging optics 20 andphotodiode 22 enables a very compact and optically precise photometerarrangement to be achieved which can be provided to the user in acompact housing 46 in order that he himself may evaluate test strips 10that are in particular designed as disposable articles. For this purposea holder 48 that can be inserted into the housing 46 is provided as apositioning unit for the test strip 10.

In the arrangement of FIG. 1 the optical path extends from the lightsource 16 through the substrate 18 and the imaging optics 20 onto thetest area 34 and is reflected or remitted there via the imaging optics20 through the substrate 18 into the detector 24. However, atransmissive arrangement is also basically possible in which the teststrip 10 is examined in the transmitted light between the light sourceand detector.

According to FIG. 1 an image of each OLED 14 is formed on a target areaon the test strip 10 by a group of lens units 36. The embodiments shownin FIGS. 2 and 3 differ therefrom essentially in that each OLED 14 hasan associated single lens 36 with a large lens diameter. According toFIG. 2 this is designed as a Fresnel lens 36′ and its design isoptimized for microstructuring and moulding technology. FIG. 3 shows anaspherical collecting lens 36″ for focussing the emitted light.

In the embodiment of FIGS. 2 and 3 special anode layers of the OLEDs 14are provided as individually controllable front electrodes while acontinuous cathode layer 30 forms a common rear electrode.

In the embodiment example shown in FIG. 4 a housing 50 is provided forhermetically screening the free surface of the OLED 14 from theenvironment in order to protect the organic light-emitting layer 26 aswell as the transport/injection layers 52 and metal electrodes 30 fromoxidation by oxygen and from the effects of moisture. The edge of thehousing 50 can be attached to the electrode layer 28 or the supportsubstrate 18 by an adhesive layer 54 and the housing can contain adesiccant 56 as an additional protection against moisture. It is obviousthat a layer or similar means can be provided together with the supportsubstrate 18 as a material-tight barrier instead of a separate housing.

A further embodiment is shown in FIG. 5 with a plurality of elementaryphotometers 58 arranged on the surface of the support substrate in amatrix-like manner. Each of the elementary photometers 58 are formed ona quadratic pixel area by a cross-shaped polymer photodiode 22 and fourOLEDs 14 arranged in the corner areas that operate with differentwavelengths where of course other local combinations are also possible.This allows a target area on the test element 10 to be optically scannedin a spatially resolved manner as illustrated in FIG. 5 by the circle60. This allows small amounts of sample to be photometrically analysedeven when the positioning is inaccurate. At the same time it alsoenables the optical measuring path to be reduced and optionally allowsone to even dispense with an imaging optics.

1. Measuring device for optically analysing especially a diagnostic testelement (10) comprising a light source (16), a photodetector (24) and adevice (12) for positioning the test element (10) in an optical pathbetween the light source (16) and photodetector (24), the light source(16) having one or more organic light-emitting diodes (QLEDs) and theOLEDs (14) forming a composite structure by means of a support substrate(18) with an imaging optics (20) and/or the photodetector (24). 2.Measuring device as claimed in claim 1, characterized in that aplurality of OLEDs (14) are arranged on the support substrate (18) as aone-dimensional or two-dimensional light-emitting pixel array. 3.Measuring device as claimed in claim 1 or 2, characterized in that theOLEDS (14) have emission wavelengths ranges that are different from oneanother.
 4. Measuring device as claimed in one of the claims 1 to 3,characterized in that the OLEDs (14) are preferably aligned in agrid-like manner on different illumination target areas.
 5. Measuringdevice as claimed in one of the claims 1 to 4, characterized in that theOLEDs (14) are composed of two electrode layers (18, 30) and anintermediate sandwich-like electroluminescent light-emitting layer (26)that is preferably formed from a polymer.
 6. Measuring device as claimedin one of the claims 1 to 5, characterized in that the OLEDs (14) have apixel size of less than 500 μm, preferably of less than 200 μm. 7.Measuring device as claimed in one of the claims 1 to 6, characterizedin that the OLEDs (14) have a transparent front electrode layer (28)adjoining the support substrate (18) and a rear electrode layer (30)facing away from the substrate.
 8. Measuring device as claimed in one ofthe claims 1 to 7, characterized in that the imaging optics (20) has atleast one optical lens (36; 36′, 36″) for forming an image of the lightsource (16) on a target area (34) of the test element (10) and/or of atarget area (34) of the test element (10) on the photodetector (24). 9.Measuring device as claimed in one of the claims 1 to 8, characterizedin that the imaging optics (20) has a plurality of microstructured,preferably aspherical lens units in a two-dimensional arrangement. 10.Measuring device as claimed in one of the claims 1 to 9, characterizedin that the imaging optics (20) is formed by a lens structure mouldedonto the support substrate (18) especially by embossing.
 11. Measuringdevice as claimed in one of the claims 1 to 9, characterized in that theimaging optics (20) is formed by a foil material, preferably apolymer-based foil material having a lens structure (38) that ispreformed especially by embossing, injection moulding or reactionmoulding that is joined to the support substrate (18) in a planarfashion.
 12. Measuring device as claimed in one of the claims 1 to 11,characterized in that the OLEDs (14) are arranged on one side and theimaging optics (20) are arranged on the opposite side of the supportsubstrate (18).
 13. Measuring device as claimed in one of the claims 1to 12, characterized in that the support substrate (18) consists of atransparent flat material especially of a thin glass or an optionallymultilayer polymer film.
 14. Measuring device as claimed in one of theclaims 1 to 13, characterized in that the photodetector (24) is formedby at least one layer-shaped organic photodiode (22).
 15. Measuringdevice as claimed in claim 14, characterized in that a plurality oforganic photodiodes (22) are arranged on the support substrate (18) aslinear or planar sensor pixel array.
 16. Measuring device as claimed inone of the claims 14 or 15, characterized in that the OLEDs (14) andoptionally the photodiodes (22) are applied to the support substrate(18) by a coating process.
 17. Measuring device as claimed in one of theclaims 14 to 16, characterized in that a plurality of OLEDs (14) andphotodiodes (22) that are locally combined as elementary photometers(58) and are arranged as a matrix on a surface of the support substrate(18), form a multiple photometer.
 18. Measuring device as claimed in oneof the claims 1 to 17, characterized in that the device (12) forpositioning comprises a holder, a guide or a stop for the test element.19. Measuring device as claimed in one of the claims 1 to 18,characterized in that the surface of the OLEDs (14) is screened from theenvironment in a material-tight manner by a coating or housing (50). 20.Measuring device as claimed in one of the claims 1 to 19, characterizedin that that the test element (10) is formed by a test strip providedwith optically scannable indicator fields (34) for biological substancesto be detected and especially a test strip designed as a disposablearticle for example a glucose test strip.